Flaw detector for tubular conductors



Feb. 6, 1934. F. D. BRADDON El AL FLAW DETECTOR FOR TUBULAR CONDUCTORS Filed July 21, 1932 2 Sheets-Sheet l FISSURE INDICATION ECCENTRIC'TV INDICATN RECTIFIER a PWER 5UPPLY AMPL'FIER g 25 m E TO g g c l'rhep rlflr.

ATTORN EY Feb. 6, 1934. F. D. BRADDON ET AL FLAW DETECTOR FOR TUBULAR CONDUCTORS FiLed July 21, 1952' 2 Sheets-Sheet 2 POWER SUPPLY l T e w I'ZIICI! ATTORNEY Patented Feb. 6, 1934 1,946,189

UNITED STATES PATENT OFFICE FLAW DETECTOR FOR TUBULAR CONDUCTORS Fred D. Braddon, Eltingville, Staten Island, and Francis H. Shepard, Jr., New Rochelle, N. Y., assignors to Sperry Products, Inc., Brooklyn, N. Y., a corporation of New York Application July 21, 1932. Serial No. 623,748

17 Claims. (01. 175183) This invention relates to a method and means cable passes out of the machine at 12. At the for testing tubular conductors, such as the lead discharge side of the lead sheath forming masheathing surrounding electric cables, and is an chine is positioned the testing apparatus 15 which improvement over the co-pending application of includes sets of guide rollers 16 and 17 for guid- Elmer A. Sperry, Jr. and Francis H. Shepard, ing the cable, the testing apparatus being intet- 60 Jr., Serial No'. 592,524 filed February 12, 1932 posed in the space between said sets of rollers. for Flaw detector for electrical conductors. As Said testing mechanism may comprise means for set forth in detail in.the said co-pending applipassing current through the sheath or for incation, the method employed consists in providducing flux therein. The latter form is here 0 ing relative rotation as well as relative axial shown and includes an induction coil 18 posi- 65 movement between the detector mechanism and tioned concentrically with the lead sheath to inthe cable so that said mechanism traverses a subduce flux therein. The detector mechanism may stantially spiral path whereby the entire circumcomprise a pair of contacts 19 operating in the ference of the lead sheath is tested. The detecregion of the induced flux to take oil a voltage tor mechanism may comprise a pair of contacts therefrom. Any variations in said voltage or flux or inductive means which will detect any variadue to fissures or eccentricity will be picked up tions in the characteristics of current fiow by the contacts 19. Spaced contacts may be prothrough the sheath, the current being supplied to vided for passing current through the lead sheath the sheath either by contacts to establish a curin place of the inducing coil 18 and induction 20 rent therethrough or by an inducing coil to induce coils may be substituted for the contacts 19 as 75 a flux. shown in the said co-pending application Serial By the use of the above method it was found No. 592,524 and in the Sperry Patent No. 1,820,505. that flaws were detected, said flaws consisting not In order that the detector mechanism may test only of fissures within the sheath but also of the entire circumference of the sheath, relative 2 eccentricities or variations of thickness of the rotation as well as relative axial movement is sheath wall. No means were shown, however, in provided. The relative axial movement may be said co-pending application for differentiating obtained by the continued passage of the lead between fissures and eccentricities. It is the covered sheath through the testingdevice 15, principal object of this invention to provide in a while relative rotation between the parts may be 30 mechanism of the type described in said co-pendobtained by mounting the contacts 19 on'a roing application means whereby separate indicatating cylinder 20 concentric with the lead sheath, tions of fissures and eccentricities may be obsaid cylinder being rotated in bearings 21 by any tained. suitable means such as a motor 22, belt 23, and

Further objects and advantages of this invenpulley 24.

tion will become apparent in.the following de- The detector mechanism now traces a spiral tailed description thereof. path on the surface of the lead sheath and In the accompanying drawings, traverses substantially the entire surface thereof.

Fig. 1 is a diagrammatic representation of our Any variations in current flow due to fissures or invention. eccentricity of the lead sheath will be picked up Fig. 2 is a front .elevation of a lead sheath by the detector mechanism and after being forming machine with our testing apparatus apamplified by the amplifier 30 may be utilized to plied thereto, the said apparatus being shown actuate relays 31, 31' and 32 which in turn may partly sectioned. 1 energize suitable indicators such as pens P, P,

Fig. 3 is a wiring diagram showing the details P" through means such as magnets 33, 33' and 0f the amplifier. 34 to make records on a chart C. 100

Fig. 4 is an enlarged view of a portion of the Heretofore, no means was provided whereby device shown in Fig. 2. fissures could be distinguished from eccentricities.

Referring to Fig. 2 of the drawings, it will be By this invention suitable means is provided for seen that our invention is designed to be applied separating the responses due to fissures from to a lead sheath forming machine which is shown those due to eccentricities, thus enabling them at 10 and through which a cable 11 is designed to to be separately indicated. Thus, in Fig. 1 it will be passed. As said cable passes through the mabe seen that there is indicated diagrammatically chine 10 an extrusion device under pressure from a constant energizing current 40 supplied to the a. hydraulic pump within machine 10 coats the inducing coil 18. The contacts 19 would pick up .5 cable 11 with lead so that the lead sheath covered a constant voltage if there were no fissures gr- 1 eccentricities present; but in the presence of fissures and eccentricities the oscillograph made by the output from such contacts is shown at 41. When this output is rectified it appears as shown at 42 and this enables one to see at once that the graph is actually a composite of two separate types of indications. One type is the sharp indication of short duration shown at '43 and is the quick impulse generated when the detector mechanism passes over a fissure, since such fissures are of slight extent. The other indication is that shown at 44 and is of relatively long duration. This latter indication is caused by an eccentricity which results in an impulse of relatively long duration as the detector mechanism passes thereover. The problem has been to separate the composite impulse obtained by the detector mechanism, as shown by the graph at 42, into the components 43. and 44 indicating respectively fissures and eccentricities.

In Fig. 3 we have shown a view similar to Fig. 1 but in which the amplifier diagram is disclosed in detail. Within this amplifier lies the mechanism whereby the fissure indications are separated from the eccentricity indications so that each may actuate its own indicator. The output from the detector mechanism 19 may be taken off slip-rings 26 by means of brushes 2'7. The potential taken ofi by brushes 27 forms the input to the amplifier at 50. After passing through rectifying and amplifying stages 51, 52 and 53, the output from said amplifier 53 is split at 59 and led into two tubes 54 and 55, the output from plate 56 of tube 53 being connected to the grids 5'7 and 58 of tubes 54 and 55, respectively.

Tubes 54 and 55 are caused to respond to short duration impulses and long duration impulses, respectively, by the following means: A feedback is provided from the output of grid 56 to the tube 54 from point 60. through condensers 62 and 63, the latter being connected to a ground 64 and the said feed-back circuit being connected at point 65 to the input grid 57. If a quick impulse passes out 'of plate 56, substantially no counteracting E. M. F.will be placed upon grid 57 by the feed-back because of the fact that condensers 62 and63 charge inversely as the frequency and therefore little or no charging of condensers 62 and 63 takes place, so that no E. M. F. is placed on grid 57 in opposition to the E. M. F. placed thereon by the output of plate 56. The quick impulse, therefore, produces an output from the plate '70 of the tube 54 through the relay '31 to energize magnet 33 and actuate pen P. Several relays, 31, 31' may be connected in parallel, said relays being of varying resistance and each relay energizing its own magnet 33, 33' to operate respective pens P,P' and thus give some indication of the intensity of the fissure. Y

, The said short-period impulse does not energize relay 32 because the output from plate 56 must first charge condenser '72 which is connected to ground, and since the extent of such charging is inversely as the frequency, no appreciable charge will be placed on condenser '72 by the short-duration impulse,- so that no E. M. F. willbe impressed on the input grid 58 and the relay 32 will not be energized.

If, now, a relatively prolonged impulse is put into the amplifier because of the presence of an eccentricity, the output from plate 56 is impressed on grid 57-of tube 54, but the long period of the impulse permits the feed-back from point 60 to charge condenser-63 and through condenser 62 and resistance 66 to place a counteracting or the flux from coil 18. As a said grid and thus limit the output from plate '10. The fissure-indicating relay or relays 33, 33' are therefore not actuated. At the same time, the long period impulse permits the output from plate 56 to charge condenser 72 and place an E. M. F. on the input grid 58 of tube 55 and thus energize relay 32 which may energize magnet 34 to actuate an indicator such as pen P".

By referring to the diagrammatic showing in Fig. 1, there is disclosed a loop formed by a portion of the collector. rings 26 between the points of contact of brushes 2'7 and the fixed connections 26 which rotate with the collector rings, the loop being completed by the wires connecting the said connections and said brushes. This loop varies in size as the collector rings and their connections 26' rotate. Because of this variable loop, variations in flux from the source of supply, and also because of the fact that the collector rings 26 cannot be made perfectly uniform in cross-section throughout the entire rings, flux from the energizing coil 18, upon reaching the said variable loop and said non-uniform rings, induces a periodic current in said loop and rings. This induced current puts an E. M. F. on the amplifier and therefore results in an indication similar to that of an eccentricity because of the opposing E. M. F. on

' said periodic variations.

In order to obviate the false indication thus obtained, we have taken two steps: fiirst, we have placed the collector rings as far removed .from the inducing coil 18 as the supporting strucrent induced by the fiux which reaches it from coil 18. Said induced current builds up a field substantially equal and opposite to that due to consequence, substantially none of the flux from coil 18 reaches the collector rings 26, and therefore none reaches the 4 hereinbefore described loop, since said rings are positioned beyond member and insulated therefrom by insulation 81, 82. Another member 83, also formed of a large mass of material of low resistance such as copper, may be applied to the outer end of the rotating member 20 on the opposite side of the collector rings to perform the same function at the other end. If desired, members 80 and 83 may be formed of one integral mass.

- In accordance with the provisions of the patent statutes, we have herein described the principle and operation of our invention, together with the apparatus which we now consider to represent the best embodiment thereof,.but we desire to have it understood that. the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while conductors such as lead sheaths of cables, comprising means for passing current therethrough,

means for detecting variations in the character-' istics of current flow, and means selectively responsive to variations due to fissures and to eccentricities.

2. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, means selectively responsive to variations due to fissures, a plurality of indicators, and means whereby said indicators are selectively actuated by said responsive means.

3. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough,

-means for detecting variations in the characteristics of current flow and means for amplifying said variations, said amplifying means having means selectively responsive to variations of different periods.

4. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, com prising means for passing current therethrough, means for detecting variations in the characteristics of current flow, means for amplifying said variations, said amplifying means having means selectively responsive to variations of different periods, a plurality of indicators, and means whereby said indicators are selectively actuated by the output of said amplifying means.

5. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, and means for amplifying said variations, said amplifying means having a plurality of output circuits, said circuits including means for rendering them selectively responsive to variations of different periods.

6. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, and means for amplifying said variations, said amplifying means having a plurality of parallel circuits, said circuits including means for rendering them selectively responsive to variations of different periods.

7. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, means for amplifying said variations, said amplifying means having a plurality of output circuits, said circuits including means for rendering them selectively responsive to variations of different periods, a plurality of indicators, and means whereby said indicators are actuated from the respective circuits.

8. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means" for detecting variations in the characteristics of current flow, and means for amplifying sa d variations, said amplifying means having a plurality of parallel circuits, said circuits including means for'rendering them selectively responsive to variations of different periods, a plurality of indicators, and means whereby said indicators are actuated from the respective circuits.

9. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, and means for amplifying .said variations, said amplifying meanshaving a plurality of output circuits, each of said circuits including a thermionic tube having an inistics of current flow, and means for amplifying said variations, said amplifying means having a plurality of output circuits, each of said circuits including a thermionic tube having an input and output, one of said circuits including a feed-back from the output to the input of the respective tube, said feed-back including a grounded condenser whereby only variations of relatively short period will come through the respective tube.

11. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, and means for amplifying said variations, said amplifying means having a plurality of output circuits, each of said circuits including a thermionic tube having an input and output, the input to one of said tubes including a grounded condenser whereby only variations of relatively long period will come through the respective tube.

12. In a detector mechanism for tubular hollow conductors such as lead sheaths of cables, comprising means for passing current therethrough, means for detecting variations in the characteristics of current flow, and means for amplifying said variations, said amplifying means having a plurality of output circuits, each of said circuits including a thermionic tube having an input and output, one of said circuits including a feed-back from the output to the input of the respective tube, said feed-back including a grounded condenser whereby only variations of relatively short period will come through the respective tube, the input to the other of said tubes including a grounded condenser whereby only variations of relatively long period will come through the respective tube.

13. In a detector mechanism for electrical conductors, an inducing coil and a source of energy therefor for inducing current in said conductor, means for detecting variations in the characteristics of current flow, means for relatively rotating said conduct-or and said detecting means, a plurality of slip-rings electrically connected to said detectingmeans, and brushes engaging said rings,

said rings being positioned beyond the range of effective influence of said coil.

14. In a detector mechanism for electrical conductors, an inducing coil and a source of energy therefor for inducing current in said conductor,

means for detecting variations in the characterbetween said coil and said rings.

16. In a detector mechanism for electrical conductors, an inducing coil and a source of energy therefor for inducing current in said conductor, means for detecting variations in the characteristics of current flow, means for relatively rotating said conductor and said detecting means, a plurality of slip-rings electrically connected to said detecting means, brushes engaging said rings, and shielding meansof low electrical resistance interposed between said rings and the flux from said coil.

17. In a detector mechanism for electrical conductors, 'an inducing coil and a source of energy therefor-for inducing current in said conductor, means for detecting variations in the characteristics of current flow, means for relatively rotating said conductor and said detecting means, a plurality of slip-rings electrically connected to said detecting means, brushes engaging said rings,

a support for the preceding mechanism, said coil and said rings being positioned at opposite ends of said support, and shielding means of low electrical resistance interposed between said rings and the flux from the said coil.

FRED D. BRADDON. FRANCIS H. SHEPARD, JR. 

